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14.2 Extended Channels (T7 Only) [T-Series Datasheet]

Overview - T7 Only

The T7 has 14 built-in analog inputs (AIN0 through AIN13). For applications that need more, up to 112 total external analog inputs can be utilized by multiplexing the built-in analog inputs. Each built-in analog channel may be multiplexed into 8 new channels, where the starting extended channel number is:

startingExtendedChannel = builtinChannel * 8 + 16

The extended channel range begins at AIN16.

When a built-in channel is multiplexed, the original channel number becomes unavailable.

For example, if AIN4 is multiplexed, AIN48 through AIN55 are exposed as usable AIN and AIN4 is no longer available.

Differential Channels Pairings

For differential channels in the extended range, a channel may be the positive channel if it is one of the following ranges:

AIN16 through AIN23

AIN32 through AIN39

AIN48 through AIN55

AIN64 through AIN71

AIN80 through AIN87

AIN96 through AIN103

AIN112 through AIN119

The negative channel is 8 higher than the positive channel. For example, the positive channel AIN48 is paired with AIN56 as the negative channel.

The differential channel pairs for the built-in AIN0 through AIN13 are adjacent even/odd pairs such that the positive channel is even and the negative channel is greater than the positive channel by 1. Since the built-in AIN are multiplexed as described above, an extended negative channel is 8 higher than its corresponding extended positive channel. For example, a valid differential extended channel pair would be a positive channel of AIN70 and AIN78 as the negative channel, since:

AIN70 maps to AIN6 and

AIN78 maps to AIN7.

For more information on differential extended channels, see the Mux80 Datasheet.

MIO

The DB37 connector has 3 MIO lines designed to address expansion multiplexer ICs (integrated circuits), allowing for up to 112 total external analog inputs. Whenever a read is done on analog input channel numbers 16 to 127, the T7 will automatically control the MIO lines to read the correct multiplexed AIN.

Mux80

The Mux80 accessory is used to multiplex AIN4 through AIN13, expanding them from 10 inputs to 80 inputs. AIN0 through AIN3 are still available (on the screw terminals of the T7). The extended channels can be read using the following registers. For further details, see the Mux80 Datasheet.

Note that when using the Mux80 board, the T7's MIO(0-2) lines are consumed for multiplexer signaling.

Other Multiplexers

If you are interested in adding multiplexers yourself, see further information in Section 2.6.1 of the U6 Datasheet. The DG408 from Intersil is a recommended multiplexer, and a convenient ±12 volt power supply is available on the DB37 so the multiplexers can pass bipolar signals (see Vm+/Vm- documentation in Section 16.0).

Differential Tables

The tables below show which channels are positive (Pos) or negative (Neg) when paired differentially.

Built-in AIN (not multiplexed):

Pos

Neg

0

1

2

3

4

5

6

7

8

9

10

11

12

13

AIN0 and AIN1 (multiplexed with an external multiplexer):

Pos

Neg

16

24

17

25

18

26

19

27

20

28

21

29

22

30

23

31

AIN2 and AIN3 (multiplexed with an external multiplexer):

Pos

Neg

32

40

33

41

34

42

35

43

36

44

37

45

38

46

39

47

AIN4 and AIN5 multiplexed with the Mux80 (or an external multiplexer):

Pos

Neg

48

56

49

57

50

58

51

59

52

60

53

61

54

62

55

63

AIN6 and AIN7 multiplexed with the Mux80 (or an external multiplexer):

Pos

Neg

64

72

65

73

66

74

67

75

68

76

69

77

70

78

71

79

AIN8 and AIN9 multiplexed with the Mux80 (or an external multiplexer):

Pos

Neg

80

88

81

89

82

90

83

91

84

92

85

93

86

94

87

95

AIN10 and AIN11 multiplexed with the Mux80 (or an external multiplexer):

Pos

Neg

96

104

97

105

98

106

99

107

100

108

101

109

102

110

103

111

AIN12 and AIN13 multiplexed with the Mux80 (or an external multiplexer):